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The effect of phase composition and morphology on high-temperature strength in the compression of Fe-Al-Si-based iron aluminides manufactured by casting was investigated. The structure and high-temperature strength in the compression of three alloys—Fe28Al5Si, Fe28Al5Si2Mo, and Fe28Al5Si2Ti—were studied. Long-term (at 800 °C for 100 h) annealing was performed for the achievement of structural stability. The phase composition and grain size of alloys were primarily described by means of scanning electron microscopy equipped with energy dispersive analysis and Electron Backscatter Diffraction (EBSD). The phase composition was verified by X-ray diffraction (XRD) analysis. The effect of Mo and Ti addition as well as the effect of long-term annealing on high-temperature yield stress in compression were investigated. Both additives—Mo and Ti—affected the yield stress values positively. Long-term annealing of Fe28Al5Si-X iron aluminide alloyed with Mo and Ti deteriorates yield stress values slightly due to grain coarsening.

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A structural studies have been performed on Fe-Al-Si iron aluminides with or without addition of chromium prepared by standard cast process. The effect of chromium addition and subsequent annealing on the phase composition was studied. Very fine precipitates were observed on the grain boundaries in the alloy without chromium addition. On the other hand, complex chromium carbides formed in the structure of chromium doped alloy. The annealing of alloy without Cr addition leads to partial dissolution of secondary phase particles. Unlike the chromium-doped alloy, where the secondary phase coarsed during the annealing process. The phase composition of the alloys was studied by means of scanning electron microscopy (SEM) equipped by energy dispersive X-ray spectrometer (EDX). The electron backscattered diffraction (EBSD) was used for phase verification.